Carburetor



oct. z2, 1957A E. OLSON ETAL 2,810,560

CARBURETOR Filed Dec. 29, 1955 AT TORNE) CARBURETOR Elmer Olson and Arthur G. Winter, Rochester, N. Y., as-

signors to General Motors Corporation, Detroit, Mich., a corporation of Delaware Application December 29, 1955, Serial No. 556,124

Claims. (Cl. 261-23) This invention relates to carburetors for internal combustion engines, particularly for automotive use and primarily to the means for supplying fuel to the mixture passages of multi-outlet or compound carburetors during idling operation of the engine.

In compound carburetors particularly of the four outlet type and one speed operation having two primary and two secondary mixture passages which are controlled by primary and secondary throttles opened sequentially it has been customary to supply fuel for idling only to the primary mixture passages. This fuel is supplied through a plurality of fuel inlets positioned adjacent each primary throttle valve and some of these inlets are supplied with fuel from idling fuel wells associated with the main fuel wells supplying fuel to the primary mixture passages, while at least one of said inlets is sup plied with fuel from secondary fuel wells which are associated with the main fuel wells which supply fuel to the secondary mixture passages during normal engine operation at highest speeds after opening of the secondary throttles. A carburetor of this construction is shown in the copending application of Olson et al., Ser. No. 264,136, filed December 29, 1951, nowiPat, No. 2,771,282, dated Nov. 20, 1956.

yIn some installations, due to certain characteristics of the engine, itself, engines with which carburetors such as described were used would not idle or run at lower speeds satisfactorily. It is the primary purpose of the present invention to eliminate the diiiiculty referred to and to modify the construction of the multi-outlet carburetor used in such installations in such a way that the engineson which such carburetors are installed will idle satisfactorily under all idling conditions and will operate satisfactorily at lower speeds before opening of the secondary throttles. It was found that this could be aecomplished by the provision-of one or more idling fuel inlets positioned posterior to each secondary throttle valve, such inlets being supplied with fuelV from secondary idle Wells which are associated with the main secondary fuel wells and which supply fuel also to one of the idle fuel inlets in each primary mixture passage.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawing, wherein l preferred forms of the invention are clearly shown.

In the drawing:

The drawing is a vertical partly diagrammatic section through a carburetor in which the idling fuel supply means is constructed in accordance with the present invention. l

Except for the specific -arrangement of the fuel supply passages which supply fuel for idling and low speed operation the carburetor illustrated herein is of exactly the same construction as that shown in the above mentioned application to which reference may be had for a complete disclosure of the entire device and only the fuel supply vsystem constituting the present invention and parts associated therewith are fully shown and described.

fic

The carburetor comprises three castings positioned one above the other, a throttle body casting 2 which is secured to the intake manifold of the engine, a fuel chamber casting 4 which is positioned above the casting 2 and an air inlet casting 6 above and supported by the casting 4. Suitable gaskets are provided between the castings to prevent leakage.

ln the casting 2 are four mixture outlet passages, only two of which are shown. There are two primary outlet passages 3 and two secondary outlet passages 10, while flow of mixture through each primary passage is controlled by a throttle valve 12 and flow through each secondary passage is controlled by a throttle valve 14. There are two valves 12, one in each primary passage, and these `are secured to a common operating shaft 16 which is actuated manually by t-he operator of the vehicle on which the carburetor is used, by means of the conventional operating connection extending Vfrom the normal foot operated accelerator pedal to the shaft 16. There are also two secondary throttles 14 both of which are secured to a common operating shaft 18, such shaft being operated by the primary throttle shaft 16, through the medium of a lost motion arrangement which does not begin opening theV secondary throttles until after a predetermined opening movement of the primary throttles. Since the design of this mechanism is of no material importance it is not shown herein, but may be of the same construction as that shown and described in the aforementioned application, and which starts to open the secondary throttles after the primary throttles have made about 40 degrees of opening movement.

The air inlet casting 6 has two air passages 20 and 22 formed therein, which supply air to the primary and secondary mixture passages respectively, each of the air passages supplying two mixture passages. Air enters passage 20 for both primary mixture passages and air enters passage 22 for both secondary mixture passages. Admission of air through the passage 20 is controlled by an unbalanced choke valve24 which is controlled automatically in accordance with variations in engine temperature, engine suction posterior to the throttles and the pressure of the entering air-.directly on the unbalanced valve itself, as fully disclosed in the earlier application.

Air entering the passage 20 ows into two channels or passages 26, only one of which is shown, but both of which are formed in the casting 4 and each of which communicates with a primary mixing chamber which communicates with one of the outlet passages 8. The secondary air passage 22 communicates with and supplies air to two chambers or passages 28 also in casting 4, only one of which is shown and each of which communicates with a secondary mixing chamber which communicates with one of the secondary outlet passages l0. Air passage 20, passage 26, the primary mixing chamber and passage form what is hereinafter termed the primary mixture passage, while passages 22, 28, the secondary mixing chamber and passage 10 form the secondary mixture passage. g

Formed inthe `casting'4 are two fuel chambers 30 and 32 to which fuel is supplied from a suitable source and is maintained at a constant level by two oats 34 and 36, indicated in dotted lines, which operate valves that stop ow of fuel into the chambers 30 and 32 when a predetermined Vfuel level is attained, inthe conventional manner. The two fuel chambers 30 and 32 are separated by a partition,V not shown, butrthere is a small passage connecting the two chambers at approximately the normal fuel level, through which fuel may flow from one to the other if the level in the two chambers changes, as in the event of tilting, such passage being fully shown and described in the` aforementioned application.

Fuel is supplied by chamber 30 to the main and idling fuel inlets for each primary mixture passage and the means for supplying fuel to each of such passages is of the same construction, one of 4such means being shown in the drawings.V As shown, fuel is conveyed from chamber 30-througha passage 38 to a well 40, and the rate of fuel'ilo'w is controlled by a calibrated metering plug 42 which is screwed into the passage 38. The well 40 is connected with a second vwell 42 by a slot 44 in a part of the casting 4 which separates the two wells. The wells 40 and 42 extend upwardly and terminate at a horizontal surface formed on the main casting 4 while a small casting 46 is secured in position on this horizontal surface by any suitable means, a gasket being `positioned between the two castings to prevent leakage.

A fuel feeding tube 48 which is suitably supported by the casting 46 extends downwardly into the well 42 and supplies fuel to a passage 50 in the small casting 46 which is open at the right end for admission of air thereto. The tube 48 is closed at the bottom and has openings in the side walls thereof, through which fuel flows from the Well into the tube 48. The well is provided with an opening 54 at the vtop connecting with the chamber 26 which Vents the well. The left end of passage 50 connects with a small venturi tube S6 forming part of the casting 46 and terminating approximately at the throat of a large venturi tube 58, the space Within which constitutes the primary mixing chamber, which forms part of the primary mixture passage.

As the throttle is moved toward open position, at some point in its opening movement, sufhcient suction is created in the small venturi and passage 50 to bring about a ilow of fuel from the well 42 into the tube 48 and from such tube into the passage 50. As long as the suction is not sufficient to cause ow from well 42 at a faster rate than it is supplied thereto, the openings 52 will not be uncovered, and fuel only will be supplied by such tube to the passage S0. As the throttle is progressively opened, the suction effective on the passage v50 may become great enough to cause the level of fuel in the well to be lowered. In such event, air will enter the'opening 54, will mix with the fuel flowing into the tube from the well, so that under such conditions a mixture of fuel and air will be supplied to passage 50 by the tube 48. This will prevent the mixture becoming too rich as the throttle approaches wide open throttle position.

It should be understood that the construction of the main fuel wells and associated fuel feeding passages for the secondary mixture passages are exactly the same as such devices for the primary mixture as will be apparent from examination of the drawings. It should also be understood that in the carburetor as actually constructed fuel flows directly from the chamber 30 into Well 42 and then into well 40 but for convenience of illustration, the construction shown is the reverse of that actually used.

When the throttles are in substantially closed position and in the first part of the opening movement of the throttles before there is sufficient suction created in therpassage 50 to effect a flow of fuel from the tube 48, all of the fuel which is supplied to the carburetor is supplied by the idling fuel system. The well 40 is a part of this system and extending downwardly into this well is a tube 60, which is supported by the casting 46, such tube fitting into a recess in the casting, in which it is secured in any desirable manner. This tube has a restricted opening 62 in the bottom end thereof and the tube, at its upper end, communicates with a passage 64 formed in the casting 46, while an opening 66 admits air to the upper end of such" passage. Connecting with 'the passage 64 is a passage 68 vwhich is formed in the wall of the casting 4 and the passage 68 connects withthe upper end .of a vertical passage 70, also .formed inthe wall of casting 4. The llower end of passage 70 connects with the upper end Vof a passage 72 formed in the wall of casting 6 and there are several small passages, or bores,

4 connecting passage 72 with the outlet passage 8, two of these being bores 74 and 76 which connect the passage 72 with the passage 8, close to the edge of the throttle valve, but anterior thereto when the throttle is in closed or idling position. As the throttle moves toward open position, the bores 74 and 76 become posterior to the edge of the throttle after a slight opening movement thereof.

A third bore 78, which is always posterior to the throttle, also connects the passages 72 and 8, and this bore is controlled by a manually adjustable valve which is screwed into the casting 2 and is held in any adjusted position by a spring v82 in the usual way. A calibrated metering plug 84 may be positioned in the upper end of the passage 72 and held in position in any suitable way, for the purpose of metering the fuel which ows through such passage to all of the bores 74, 76,and 78. Also positioned in a bore 86 which connects the passage 70 with the main mixing chamber is a tube 88, one end of which is cut olf at an angle as indicated in the drawing. This tube has a tight lit in the bore 86, but may be rotated therein to adjust the position of the angled end of the tube with reference to path of flow through the mixing chamber. By changing the position of the tube, the degree of suction in the passage 70 may be controlled to some extent.

As already pointed out, the arrangement of fuel wells associated with the secondary mixture passage and the construction of the main fuel feeding means therefor is just the same as that for the primary passages. However, the idling fuel system is not quite the same, although the construction of the idle Wells, themselves, is just the same. The secondary idle well which is shown in the drawing is designated 90. A tube 92 depends from a casting 94 similar to casting 46 and this tube connects with a passage 96 in such casting. A passage 98 connects the passage 96 with a horizontal groove 100 formed in the lower face of the casting 4. This groove extends toward the secondary mixture passage and then around such passage, as indicated in the drawing, to a point between the primary and secondary mixture passages, where it connects with a vertical passage 102 which extends downwardly to a point just below the primary and secondary throttle valves. A bore 104 connects the passage 102 with the primary outlet passage 8 just posterior to the throttle 12 when the latter is closed and this bore will be anterior to the throttle afterthe latter has made a very slight opening movement. `A tube 106, similar to tube 88, connects the passage 102 with the mixing chamber 58 and functions in the same way'as does the tube 88. A metering plug 108 similar to the plug 84 meters the fuel flowing through the passage 102.

The mechanism so 'far described is substantially the same in construction as that disclosed in the aforementioned application andin most installations this mechanism has proven entirely satisfactory under all operating conditions both idling and-operation after the throttle is opened and the engine is under load. However, as already indicated, in some installations, because of engine characteristics, 'the device described would not produce satisfactory idling or operation under load at such speeds as are reached before the secondary throttles are opened and, in order to obtain satisfactory operation under the conditions referred to, it was found necessary to introduce fuel into the secondary mixture passages posterior to the secondary throttles so that such fuel will be available to be carried into the engine, not only during idling operation, but also after the primary throttles have been opened suiiiciently to render the primary idling system substantially ineffective.

Therefore, according to the present invention, a passage 110 is formed in the wall of the casting 2 adjacent the secondary outlet passage 10, which connects at its upper end with the groove 100 and at thelowerend of such passage itis connected by a bore 112 with the passage immediately posterior to the secondary throttle 14. Also another bore 114 connects the passage 102 with the opposite side of the passage 10 adjacent, but posterior to the secondary throttle 14. These bores 112 and 114 will supply fuel to the secondary outlet passages not only when the throttles are closed, but also during the opening of the primary throttles until the secondary throttles are also opened, but at a decreasing rate as the primary throttles move toward open position.

It should be apparent that the action of the bores 112 and 114 prior to the opening of the throttles 14 is very different from that of the idling fuel inlets associated with the primary passages. As the primary throttles open, the suction on the idling fuel inlets associated with the primary passages decreases and the ow of fuel therefrom also decreases. Ultimately as the throttle opens enough suction will be communicated to the passage 50 to cause the main fuel supply to function. During a small part of the throttle movement there may be a flow of fuel from both main and idling fuel inlets, but when the throttle moves far enough, the suctionon the main jet gets so great that there is a reverse ow through the idling fuel passages and the idling system ceases to function at all.

As the primary throttles are opened, the suction in the secondary outlet passages posterior to the throttles decreases also, because the suction in the manifolds with which all 0f the outlet passages connect is decreased by the admission of air through the primary mixture passages. However, there is enough suction to effect a liow from the bores 112 and 114. With the secondary throttles closed, there is substantially atmospheric pressure maintained anterior to such throttles, so that there is no force effective to create a reverse flow in the passage 100 and it requires very little suction to effect a ow of fuel from either main or idling fuel systems. Therefore, fuel will continue to ow from the bores 112 and 114 long after it ceases to flow from the several fuel inlets of the idling fuel system which are associated with the primary passages.

ln View of the foregoing, it is apparent that fuel will be supplied to the secondary outlet passages between the throttle and the engine, not only during idling, but also during operation under load in the lower speed ranges. The quantity of fuel thus supplied decreases as the primary throttles are opened and the speed increases, and nally ceases when the secondary throttles are opened. The arrangement described effectively eliminated the diiculty, previously referred to, which had been encountered with certain engines and brought about satisfactory operation of such engines under all conditions, either When idling or operating under load.

It should also be understood that the present invention, although intended particularly for a four-outlet carburetor, can be embodied in a dual carburetor, having only one primary mixture passage and outlet with one secondary mixture passage and outlet.

It should also be understood that while it is preferable and better fuel is secured by the provision of two fuel inlets in the secondary mixture passage, such as 112 and 114, on opposite sides of the secondary mixture passage, in some installations both passages are not really necessary and one passage can be omitted, but somewhat better results are secured when both passages are provided.

While the embodiment of the present invention as herein disclosed, constitutes a preferred form, it is to be understood that other forms might be adopted.

What is claimed is as follows:

1. A compound carburetor, having primary and secondary mixture passages, a main fuel inlet for each mixture passage, means admitting air to said passages, a primary throttle controlling the flow of combustible mixture from the primary mixture passage, a secondary throttle for controlling the flow of mixture from the secondary mixture passage and movable toward open position only after a predetermined opening movement of the primary throttle, an idling fuel supply passage, idling fuel inlets connecting said fuel supply passage with the primary mixture passage adjacent the primary throttle and effective to supply fuel only when the primary throttle is in its normal idle position and during a part of its opening movement, a second idling fuel supply passage, a plurality of fuel inlets located posterior to the throttle on opposite sides of the secondary mixture passage for connecting the latter with said second fuel passage, said last named fuel inlets being effective to supply fuel to the secondary mixture passage during idling of the engine and operation under load.

2. A compound carburetor, having primary and secondary mixture passages, a main fuel inlet for each mixture passage, means admitting "air to said passages, a primary throttle controlling the ow of combustible mixture from the primary mixture passage, a secondary throttle for controlling the -llow of mixture from the secondaryy mixture passage and movable toward open position only after a predetermined opening movement ofthe primary throttle, a primary idling fuel well, an idling fuel supplyv passage communicating with said well, a plurality of idling fuel inlets connecting said idling fuel passage with the primary mixture passage only, a secondary idling fuel Well, a second idling fuel supply passage connecting with said secondary well and a plurality of fuel inlets for connecting said second fuel supply passage with both the primary and secondary mixture passages.

3. IIn a compound carburetor having a plurality of primary mixture passages and a plurality of secondary mix- .ture passages for supplying a combustible fuel and air mixture to the engine, means for admitting air to all of said passages, a primary throttle in each of said primary passages and a secondary throttle in each of the secondary passages movable toward open position only after a predetermined opening -movement of the primary throttles and a main fuel inlet in each of said mixture passages after the throttles in each of said mixture pasasges has been partially opened, an idling fuel supply passage for supplying fuel to each of said primary mixture passages, idling fuel inlets for connecting each of said fuel supply passages with the primary mixture passage receiving fuel therefrom and positioned adjacent the primary throttle in such mixture passage, said fuel inlets being effective to supply fuel to the associated primary mixture passage only when the primary throttle therein is in its normal idle position and during a part of its opening movement, a secondary idling fuel supply passage associated with each of said secondary mixture passages, a plurality of fuel inlets connecting each of said secondary fuel supply passages With one of the secondary mixture passages posterior to the throttle therein and on opposite sides of the secondary mixture passage, said fuel inlets being operative to supply fuel to the associated secondary mixture passage as long as the throttle therein remains closed, irrespective of the position of the primary throttles.

4. In a compound carburetor hav-ing a plurality of primary mixture passages and a plurality of secondary mixture passages for supplying a combustible fuel and air mixture to the engine, means for admitting air to all of said passages, a primary throttle in each of said primary passages and a secondary throttle in each of the secondary passages movable toward open posit-ion only after a predetermined opening movement of the primary throttles and a main fuel inlet in each of said mixture passages after the throttles in each of said mixture passages has been partially opened, an idling fuel supply passage for supplying fuel to each of said primary mixture passages, a primary idling fuel well for each of said primary mixture passages, a primary fuel supply passage for conveying fuel from each of said wells to one of the primary mixture passages, a plurality of fuel inlets for connecting the primary fuel supply passage with its associated primary mixture passage and positioned adjacent the throttle therein, a secondary idling fuel well for each of said secondary mixture passages, a secondary fuel supply passage connecting with each of said secondary idling vvells and a plurality of fuel inlets for connecting said secondary fuel passage with one of said secondary mixture passages and also with one of the primary mixture passages.

5. In a compound carburetor having a plurality of primary mixture passages and a plurality of secondary mixture passages for supplying a combustible fuel and air mixture to the engine, means for admitting air to all of said passages, a primary throttle in each of said primary passages and a secondary throttle in each of the secondary passages movable toward open position only after a predetermined opening movement of the primary throttles and a main fuel inlet in each of said mixture passages after the throttles in each of said vmixture passages has been partially opened, an idling fuel supply passage for supplying fuel to each of said primary mixture passages, a primary idling fuel Well for each of said primary mixture passages, a primary fuel supply passage for conveyt ing fuel from each of said wells to one of the primary mixture passages, a plurality of fuel inlets for connecting the primary fuel supply passage with its associated primary mixture passage andpositioned adjacent the throttle therein, both posterior and anterior thereto, asecoudary idling fuel `Well for each of said secondary-mixture passages, a secondary fuel supply passage connecting with each of said secondary idling Wells, and ay plurality of fuel inlets for connecting said secondary fuel passage with one of said secondary mixture passages and also with one of the primary mixture passages, all of said last named fuel inlets being located posterior to the throttles in the mixture passages with which said fuel inlets communicate.

References Cited in the file of this patent UNITED STATES PATENTS 1,906,278 Montgomery May 2, 1933 2,315,183 Bicknell et al. Mar. 30, 1943 2,390,019 Winkler et al. Nov. 27, 1945 2,728,563 Henning Dec. 27, 1955 2,745,645 Kittler et al. May 15, 1956 

